One atomic mass unit is equal to the mass of a carbon-12 atom
One atomic mass unit is equal to the mass of a carbon-12 atom.
112. The relative atomic mass of an element is the average mass of its individual isotopes, considering the relative abundance of each.
113. Lithium is composed of two isotopes: lithium-6 and lithium-7. Lithium-7 is the more abundant of the two isotopes.
114. The mass of exactly 100 carbon atoms is 12.01 amu.
115. The mass of exactly 1000 magnesium atoms is 2.431 ? 104 amu.
116. Mendeleev arranged his periodic table in order of increasing atomic number.
117. Mendeleev was able to predict the existence of unknown elements using his periodic table.
118. The modern periodic table is arranged in order of increasing atomic mass.
119. Elements within a vertical column of the periodic table are called a family or group.
120. A horizontal row of the periodic table is called a period.
121. A metalloid is an element that has physical properties similar to those of a metal, but chemical reactivity which more closely resembles a nonmetal.
122. Elements in the eight groups labeled “A” are transition elements.
123. Elements in group IIA (2) are called alkali metals.
124. There are seven elements that occur naturally as diatomic molecules.